From aba24888d9af19e0bd1c7e7344fd27841611d7a8 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 10 Oct 2015 16:00:56 -0400 Subject: [PATCH] tty: r3964: Replace/remove bogus tty lock use The tty lock is strictly for serializing tty lifetime events (open/close/hangup), and not for line discipline serialization. The tty core already provides serialization of concurrent writes to the same tty, and line discipline lifetime management (by ldisc references), so pinning the tty via tty_lock() is unnecessary and counter-productive; remove tty lock use. However, the line discipline is responsible for serializing reads (if required by the line discipline); add read_lock mutex to serialize calls of r3964_read(). Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_r3964.c | 20 +++++++++++++------- include/linux/n_r3964.h | 5 +++-- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/drivers/tty/n_r3964.c b/drivers/tty/n_r3964.c index 6fdef921cdb7..345111467b85 100644 --- a/drivers/tty/n_r3964.c +++ b/drivers/tty/n_r3964.c @@ -978,6 +978,7 @@ static int r3964_open(struct tty_struct *tty) } spin_lock_init(&pInfo->lock); + mutex_init(&pInfo->read_lock); pInfo->tty = tty; pInfo->priority = R3964_MASTER; pInfo->rx_first = pInfo->rx_last = NULL; @@ -1063,7 +1064,16 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, TRACE_L("read()"); - tty_lock(tty); + /* + * Internal serialization of reads. + */ + if (file->f_flags & O_NONBLOCK) { + if (!mutex_trylock(&pInfo->read_lock)) + return -EAGAIN; + } else { + if (mutex_lock_interruptible(&pInfo->read_lock)) + return -ERESTARTSYS; + } pClient = findClient(pInfo, task_pid(current)); if (pClient) { @@ -1075,7 +1085,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, goto unlock; } /* block until there is a message: */ - wait_event_interruptible_tty(tty, tty->read_wait, + wait_event_interruptible(tty->read_wait, (pMsg = remove_msg(pInfo, pClient))); } @@ -1105,7 +1115,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file, } ret = -EPERM; unlock: - tty_unlock(tty); + mutex_unlock(&pInfo->read_lock); return ret; } @@ -1154,8 +1164,6 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file, pHeader->locks = 0; pHeader->owner = NULL; - tty_lock(tty); - pClient = findClient(pInfo, task_pid(current)); if (pClient) { pHeader->owner = pClient; @@ -1173,8 +1181,6 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file, add_tx_queue(pInfo, pHeader); trigger_transmit(pInfo); - tty_unlock(tty); - return 0; } diff --git a/include/linux/n_r3964.h b/include/linux/n_r3964.h index e9adb4226224..90a803aa42e8 100644 --- a/include/linux/n_r3964.h +++ b/include/linux/n_r3964.h @@ -161,8 +161,9 @@ struct r3964_info { unsigned char last_rx; unsigned char bcc; unsigned int blocks_in_rx_queue; - - + + struct mutex read_lock; /* serialize r3964_read */ + struct r3964_client_info *firstClient; unsigned int state; unsigned int flags; -- 2.20.1